The insulation of wall cavities is known in the art. For example, it is known to position insulating fiberglass batts in vertical wall cavities of a home or building in order to insulate the wall. Such insulation helps reduce the amount of heat which can escape a home or building to the outside in winter months for example. In addition to the use of fiberglass insulation, other types of insulation are also known such as cellulose insulation an foam insulation. These types of insulation have even been combined in certain instances.
It has been found by the instant inventors that the flow of air through fiberglass insulation has a significant detrimental effect on the R-value or thermal performance of the insulation, especially in cold weather conditions. In particular, it has been found that the flow of air through fiberglass can significantly decrease the effective R-value of the insulation in a vertical wall cavity or the like.
In certain example embodiments of this invention, a dynamic heat flow meter, and method, is/are provided for testing thermal properties of fiberglass inclusive insulation materials including apparent thermal conductivity and/or heat capacity. Thermal properties, such as thermal conductivity, are important physical properties of insulation or the like. Heat flows through insulation that has a temperature gradient across its volume. The thermal conductivity of a specimen can be measured directly by measuring the heat flux resulting from a known temperature gradient across a known thickness of the material.
A one-dimensional form of the Fourier heat flow relation is sometimes used to calculate thermal conductivity under steady-state conditions: k=Q(ΔX/ΔT), where “k” is thermal conductivity, “Q” is a heat flow per a unit surface area (heat flux), and ΔT is a temperature difference over the thickness ΔX. Prior Art FIG. 1 illustrates a conventional static heat flow meter for measuring the thermal conductivity of a test sample (e.g., piece of insulation such as fiberglass). The test sample or specimen is located between two flat plates, and the plates are maintained at known, but different, temperatures. As heat flows through the test sample from the hot side to the cold side, a heat flux transducer (not shown) measures the amount of heat transferred. Thermocouple(s) or other temperature measuring device(s) measure the temperatures of each of the two plates (i.e., of the so-called hot and cold plates). These values are then plugged into the above-listed equation, so that the thermal conductivity of the test sample or specimen can be calculated based on the measured values. Such measurements are often done in accordance with standard testing methods such ASTM C 518, which is incorporated herein by reference. It is in such a manner that insulation products such as fiberglass batts are assigned so-called “R-values”—based on their steady state or static measured thermal properties per ASTM C 518 (e.g., R11 fiberglass insulation batt, etc.).
Unfortunately, the standard testing device of FIG. 1 discussed above determines thermal properties of the test sample via steady state or static testing, where there is no air flow (i.e., there is zero air movement introduced into the testing equipment during the testing). Thus, measurements from such devices can be deceiving as will be explained below, because they do not measure the effects of air flow through the insulation.
When insulation (e.g., fiberglass insulation batt, fiberglass loose-fill, combination/laminate of fiberglass and foam insulation, or the like) is provided in a vertical wall cavity of a home (e.g., between two-by-four studs as is known in the art), it has been found that air flow (e.g., due to wind or the like in the environment surrounding or adjacent to the home) through the wall can have an adverse effect on insulation properties. Contributions to total building heating or cooling load include the change in enthalpy of air moving through an insulation (e.g., fiberglass) and the heat flux through the insulation due to the imposed thermal gradient. The two effects are not independent since the air movement affects the temperature distribution in the insulation. One may experience an example of air flow in an exterior wall of a home by feeling a cool draft in the winter when one puts his or her hand adjacent an electrical outlet. Such air flows in or through walls, or through fiberglass insulation, can reduce the thermal performance of insulation, since insulation such as fiberglass is not an air barrier as it does not stop air flow.
As explained above, unfortunately, the conventional heat flow meter shown in FIG. 1 and discussed above does not take air flow into account when measuring thermal properties of the test sample.
According to certain example embodiments of this invention, a heat flow meter, and/or method, is/are provided for measuring thermal properties of a product (e.g., insulation product) in a manner which takes into account dynamic air flow. For example, the effect of air flow through fiberglass insulation (e.g., a batt of fiberglass insulation) can be measured. In certain example embodiments, a heat flow meter is provided which introduces a measured air flow into the system adjacent the test sample (e.g., fiberglass insulation product) to be measured. The heat flow meter then measures thermal properties (e.g., thermal conductivity and/or heat capacity) of the insulation taking into account air flow through the test sample.
By taking into account intentionally introduced and measured air flow, temperature and/or moisture/humidity content of such air flow through and/or across the insulation (e.g., fiberglass insulation), one can determine how effective the particular sample would be in real-world conditions where wind (and thus air flow in/through home walls) is a frequent occurrence. This permits one to determine which types of insulation may be effective in certain types of environments. This also permits one to determine the shortcomings of certain insulation products such as fiberglass batts in certain conditions such as cold weather conditions.
Once the disadvantages of the insulation product (e.g., fiberglass insulation batt or the like) are known via the dynamic heat flow meter which takes into account air flow through the insulation (e.g., once it is determined how much R-value is adversely affected by such air flow through the insulation), the overall insulation of a wall cavity or the like can be adapted to take these disadvantage(s) into account. For example, a sufficient amount of foam insulation may be provided in the vertical wall cavity so as to prevent or reduce air flow through the fiberglass, thereby compensating or substantially compensating for the adverse effects of air flow through the fiberglass and permitting the intended R-value(s) to be maintained or substantially maintained. In certain example instances, for purposes of example and without limitation, foam insulation having a thickness of from about one-quarter inch to three-quarters of an inch may be provided in a vertical wall cavity behind the fiberglass insulation in certain example instances, to reduce air flow through the fiberglass thereby compensating for the adverse effects of air flow through the fiberglass and permitting the intended R-value(s) to be maintained or substantially maintained. In other example embodiments, the foam insulation may be from about one quarter inch to about one and a half inches thick.
In certain example embodiments of this invention, there is provided a method of insulating a wall cavity, the method comprising: determining thermal properties of a fiberglass batt including effects of air flow through the fiberglass batt; and after determining the thermal properties of the fiberglass batt including the effects of air flow through the fiberglass batt, adapting an insulation system in a wall cavity to compensate, or substantially compensate, for the effects of air flow through the fiberglass batt by providing foam insulation in the wall cavity and then providing a fiberglass batt in the cavity over the foam insulation, wherein the foam insulation is of sufficient thickness and R-value to compensate, or substantially compensate, for the effects of air flow through the fiberglass batt.
In other example embodiments of this invention, there is provided a method of compensating for effects of air flow with respect to fiberglass insulation, the method comprising: determining or considering thermal properties of a fiberglass insulation product including effects of air flow on the fiberglass insulation; and based on at least the effects of air flow on the fiberglass insulation, providing an insulation system in a wall cavity in a manner so as to compensate, or substantially compensate, for the effects of air flow with respect to the fiberglass insulation by providing foam insulation in the wall cavity and then providing the fiberglass insulation in the cavity over the foam insulation, wherein the foam insulation is of sufficient thickness and R-value to compensate, or substantially compensate, for the effects of air flow through the fiberglass insulation.
In other example embodiments of this invention, there is provided a method of compensating for effects of air flow with respect to fibrous insulation such as fiberglass, cellulose or rock wool, the method comprising: determining or considering thermal properties of a fibrous insulation including effects of air flow on the fibrous insulation; and based on at least the effects of air flow on the fibrous insulation, providing an insulation system in a wall cavity in a manner so as to compensate, or substantially compensate, for the effects of air flow with respect to the fibrous insulation by providing foam insulation in the wall cavity and then providing the fibrous insulation in the cavity over the foam insulation, wherein the foam insulation is of sufficient thickness and R-value to compensate, or substantially compensate, for the effects of air flow through the fibrous insulation.
In still further example embodiments of this invention, there is provided an insulated wall cavity, comprising: a wall cavity; and foam insulation in the wall cavity and a fiberglass batt in the cavity over the foam insulation, wherein the foam insulation is of sufficient thickness and R-value to compensate, or substantially compensate, for the effects of air flow through the fiberglass batt.